Canadian Forest Service Publications

Response of southwest Yukon forests to spruce beetle: 2010 plot re-assessment. 2014. Hawkes, B.; Alfaro, R.; Waring, V.; Berg, J. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, British Columbia. Information report BC-X-435. 38p.

Year: 2014

Available from: Pacific Forestry Centre

Catalog ID: 35443

Language: English

Series: Information Report (PFC - Victoria)

CFS Availability: PDF (download)

Abstract

In 2000 and 2002, 27 Forest Assessment plots were established within the area infested by spruce bark beetle, Dendroctonus rufipennis Kirby (Coleoptera: Scolytidae) in southwest Yukon. The study objective was to document long-term changes in white spruce (Picea glauca (Moench) Voss) mortality, stand structure, regeneration, surface vegetation, and surface woody fuel load (Garbutt et al. 2006). A partial re-measurement was conducted in 2010, which included 22 of the original 27 FA plots. Eight of the 22 FA plots were sampled to determine growth release of spruce overstorey and understorey, and establishment of regeneration. A number of plot maintenance activities were completed to ensure future re-measurements. Forest assessment plots were prioritised and buffered for long-term protection from forest management activities. Field sampling methodology followed the protocol used in Garbutt et al. (2006) except for spruce advanced regeneration and seedlings.

Overstorey spruce and deciduous species diameter-at-breast height increased from 18.2 cm to 18.9 cm. Overstorey spruce stand density (live and dead) increased from 1059 to 1124 stems per ha and volume from 184.4 to 198.7 m3/ha. The volume of healthy overstorey spruce declined from 65.9 to 49.4 m3/ha. Growth responses in live residual overstorey spruce were detected in four of eight plots. Fifty-nine percent of the spruce seedlings sampled were established between 2000 and 2008. Establishment dates of understorey and advanced regeneration suggested continuous spruce regeneration with a few decadal pulses detected in the 1820s and 1980s. Spot fire potential increased due to loose bark on the dead spruce. Coarse woody debris load remained similar to that reported in Garbutt et al. (2006) because few dead spruce had fallen over. A complete plot re-measurement should be considered starting in 2015 and include all attributes measured in Garbutt et al. (2006) and the 2010 re-measurement.

Plain Language Summary

Since 1994, a record-breaking spruce bark beetle epidemic has been killing large areas of white spruce forests in southwest Yukon. This outbreak is impacting local economies and ecosystem functioning, and increasing the forest fire risk. In early 2000, researchers from Natural Resources Canada created Forest Assessment plots within the infestation area. They measured several attributes of the forest to monitor the impacts of the spruce beetle outbreak. In 2010, researchers re-assessed some of these plots to measure the white spruces’ recovery. They also recorded, photographed, and replaced plot markers to protect the study sites from outside disturbances such as logging and firewood cutting. This information report presents the data measured in 2010, and outlines the changes within the spruce beetle impacted forest from mature trees to tree seedling establishment. Land managers in the Yukon are already developing forest monitoring and management practices and policy using the sampling method and results from this study. The researchers recommend a complete re-measurement in 2015.

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